1 icmp vulnerability, 2 illegal commands (netbios and smtp), Figure 56 smurf attack – ZyXEL Communications 662HW Series User Manual

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Prestige 662H/HW Series User’s Guide

149

Chapter 13 Firewalls

amount of ICMP echo request and response traffic. If a hacker chooses to spoof the
source IP address of the ICMP echo request packet, the resulting ICMP traffic will not
only clog up the "intermediary" network, but will also congest the network of the spoofed
source IP address, known as the "victim" network. This flood of broadcast traffic
consumes all available bandwidth, making communications impossible.

Figure 56 Smurf Attack

13.4.2.1 ICMP Vulnerability

ICMP is an error-reporting protocol that works in concert with IP. The following ICMP types
trigger an alert:

13.4.2.2 Illegal Commands (NetBIOS and SMTP)

The only legal NetBIOS commands are the following - all others are illegal.

All SMTP commands are illegal except for those displayed in the following tables.

Table 40 ICMP Commands That Trigger Alerts

REDIRECT

TIMESTAMP_REQUEST

TIMESTAMP_REPLY

ADDRESS_MASK_REQUEST

ADDRESS_MASK_REPLY

Table 41 Legal NetBIOS Commands

MESSAGE:

REQUEST:

POSITIVE:

VE:

RETARGET:

KEEPALIVE:

This manual is related to the following products:

662H Series